3B SCIENTIFIC PHYSICS U40205 Instructions D'utilisation page 9

3B SCIENTIFIC ® PHYSICS
Operating instructions
04/10 ALF
The Cavendish torsion balance is for demonstrating
the gravitational attraction between two masses and
determining the gravitational constant.
The key component of the torsion balance is a
torsional pendulum, consisting of a supporting beam
suspended horizontally from a thin tungsten wire and
bearing two small lead spheres. The apparatus is
moved from its equilibrium position by the
gravitational force exerted on the two small spheres
by two larger spheres. If the larger spheres are moved,
the torsion balance will be drawn out of equilibrium
and will oscillate around the new equilibrium
position. The motion itself can be measured using a
Cavendish Torsion Balance U40205
1. Description
capacitive differential sensor, which largely suppresses
the noise and vibration from the signal, and displayed
on a computer. To evaluate the results further, the
data can be exported to a spreadsheet program.
Alternatively, the movement can be demonstrated
with the help of a laser pointer.
Thanks to the short period of oscillation, between 2
and 4 minutes depending on the length of the
tungsten wire, the gravitational constant can be
measured within the time span of a school lesson to
an accuracy better than 10%.
1